Suicide is a major cause of death among adolescents and those who self-harm are at increased risk of suicide. In a recently published study of suicide, hospital-treated self-harm and self-harm in the community among Irish adolescents, the ‘iceberg’ analogy was used to illustrate the relative incidence of adolescent suicide (highly visible), hospital-treated self-harm (less visible) and self-harm in the community (largely hidden).1

The study population consisted of adolescents (aged 15 to 17 years) in counties Cork and Kerry in Ireland. Annual suicide rates were calculated using data from the Central Statistics Office (based on figures from 1997 to 2011). Data on hospital-treated self-harm (between 2003 and 2011) were obtained from the National Registry of Deliberate Self-Harm which collects data on self-harm presentations in all 40 hospital emergency departments in the Republic of Ireland. Data on self-harm in the community were collected as part of the Child and Adolescent Self-Harm in Europe (CASE) study through a cross-sectional survey of 3,881 adolescents in the area in Cork and Kerry (conducted between 2003 and 2004).

The annual suicide rate among adolescents aged 15, 16 or 17 in the selected area was 10/100,000. The rate among boys was 16.5/100,000, among girls 2.7/100,000. The incidence ratio of male to female was 6:1. The incidence of hospital-treated self-harm cases was 344.4/100,000. For boys the rate was 256.2/100,000, for girls 438.1/100,000, giving an incidence ratio of male to female of 1:1.7.

Of the respondents to the CASE survey, 8.9% of girls and 2.4% of boys reported self-harm within the past year. The rate of self-harm was 5,551/100,000. The rate among boys was 2,400/100,000, among girls 8,900/100,000. The incidence ratio of male to female was 1:3.7.

Based on these incidence rates, the frequency of suicide and self-harm were calculated. For every adolescent suicide there were 34 hospital presentations with self-harm and 555 adolescents reported having self-harmed. Among boys, for every suicide there were 16 cases of hospital-treated self-harm and 146 self-reports of self-harm. Among girls, for every suicide there were 162 cases of hospital-treated self-harm and 3,296 self-reports of self-harm.

Of the 37 suicides among adolescents aged between 15 and 17 years between 1997 and 2011, four were by overdose, 31 by hanging, one by drowning and one by other methods. Of the 775 cases of hospital-treated self-harm in the same age group between 2003 and 2011, 509 (66%) were overdoses, 146 (18.8%) self-cutting, 66 (8.5%) other methods and 27 (3.5%) overdose combined with self-cutting. Of the 207 cases of adolescents reporting self-harm in the community in 2003/04, 55 (27%) were overdoses, 121 (58.5%) self-cutting and 20 (7%) overdose combined with self-cutting.

The study concluded that there are large gender differences in the incidence of self-harm and suicide among adolescents, with boys who have a history of self-harm at particular risk of suicide. However, the majority of self-harm was unreported. The need for interventions to promote awareness of mental health issues and enhance help-seeking behaviours among adolescents was highlighted.